ACCELERATION/DECELERATION CONTROL SYSTEM OF NUMERIC CONTROLLER

Abstract: This invention relates to an acceleration/deceleration control system of a numeric controller for effecting acceleration/deceleration control of a tool in the vicinity of a stroke end. The system makes it possible to move the tool by utilizing the stroke to maximum. The tool moves along a path (1) within a region (20) encompassed by a stroke end (2), and executes machining such as cutting. The movement of the tool is effected by the numeric controller in accordance with a machining program. The tool starts from the start point (P1) and moves along machining blocks (N1, N2, ..., N10) to an end point (P2). The tool moves on the basis of ordinary feed speed control in zones other than the machining blocks (N5 and N6). In the zone of the machining block (N5) near the stroke end (2), however, the tool is decelerated to a very low speed before it reaches a point (P3) of the stroke end (2). After moving from a point (P3) to a point (P4), the tool goes outside the stroke end (2). It is again accelerated according to the ordinary feed speed control when entering the block (N6) again.

Description: TECHNICAL FIELD The present invention relates to an acceleration/deceleration control apparatus for a numerical control apparatus, and more specifically, to an acceleration/deceleration control apparatus for a numerical control apparatus for carrying out an acceleration/deceleration control of a tool in the vicinity of a stroke end. BACKGROUND ART Conventionally, a numerically controlled machine tool is arranged such that when a tool is going to move beyond the stroke end set by a limit switch of a machine tool or when the tool is going to enter the prohibited region of a stored stroke limit designated by a program or setting data, an error code is displayed as well as the tool is decelerated and stopped. Nevertheless, according to this method, since the tool cannot stop at the stroke end if a sufficient distance necessary to deceleration and stop is not set, a region in which machining can be carried out is set smaller than the size of a stroke. That is, there is a problem that the region in which machining can be carried out is restricted more smaller than a region set by an intrinsic stroke end of a machine tool. JP-A-59016008 discloses an NC system with pre-movement inhibition checking. DE-A-2628961 discloses a method for varying the feed rate of a machine tool dependent upon the determination of a stroke end. Taking the above into consideration, an object of the present invention is to provide an acceleration/deceleration control apparatus for a numerical control apparatus capable of moving a tool by making maximum use of a stroke. To solve the above problem according to the present invention, there is provided an acceleration/deceleration control apparatus for a numerical control apparatus for carrying out acceleration/deceleration control of a tool in the vicinity of a stroke end, the apparatus comprising: stroke end determination means for determining whether or not said tool has moved beyond said stroke end; and: tool feed speed control means for controlling a feed speed of said tool so that the feed speed of said tool is set to a minute speed in the vicinity of said stroke end when said stroke end determination means determines that said tool has moved beyond said stroke end; characterised in that: the stroke end determination means makes a determination based upon a pre-read machining block; and said tool feed speed control means determines the feed speed of said tool using a deceleration distance determined from a maximum feed speed of said tool, said minute speed and an acceleration constant. The stroke end determination means determines whether or not the tool moves beyond the stroke end based on the pre-read machining block. When the stroke end determination means determines that the tool moves beyond the stroke end, the tool feed speed control means controls the feed speed of the tool so that the tool moves at the minute speed in the vicinity of the stroke end. The feed speed of the tool is controlled according to the control and the tool moves at the minute speed in the vicinity of the stroke end. As a result, the tool does not go across the stroke end and moves in the region within the stroke end at all times. Consequently, the tool can be moved by making maximum use of the stroke without restricting the stroke end to a small region. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an overall arrangement of an acceleration/deceleration control apparatus of a numerical control apparatus according to the present invention; FIG. 2 is a view explaining feed of a tool according to the present invention; FIG. 3 is a graph explaining a deceleration distance and an acceleration constant when a tool approaches a stroke end; and FIG. 4 is a flowchart showing a processing sequence of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a view explaining feed of a tool according to the present invention. In FIG. 2, a stroke end 2 defines the border of movement of a tool mounting axis of a numerically controlled machine tool and a region beyond the stroke end 2 is set as a prohibited region 30. A tool moves along a locus 1 in an in-stroke region 20 surrounded by the stroke end 2 and carries out machining of a workpiece such as cutting and the like thereof. The tool, which is moved by a numerical control apparatus according to a machining program, starts from a start point P1 and moves up to an end point P2 according to machining blocks N1, N2, ..., N10. The tool moves based on a usual feed speed control except the sections of the machining blocks N5, N6, and a feed speed of the tool is decelerated in the section of the machining block N5 where the tool approaches the stroke end 2 and controlled to a minute speed. The tool, whose feed speed is controlled to the minute speed just before the tool reaches the point P3 of the stroke end 2, comes into contact with the stroke end 2 at the point P3 and moves along the stroke end 2 and then leaves the stroke end 2 at a point P4. The tool is accelerated again in the section of the machining block N6 and returns to a usual feed speed control. Next, a deceleration distance and an acceleration constant when the tool approaches the stroke end 2 will be described. FIG. 3 is a graph explaining a deceleration distance and an acceleration constant when a tool approaches a stroke end. In FIG. 3, a tool feed speed F is decelerated from a maximum seed F max to a minute speed F min along a line A and reaches the minute speed F min at a time t1 and the tool moves at the minute speed F min up to a time t2. The tool reaches the point P3 of the stroke end 2 at the time t2. A distance L10 which the tool moves from the time t1 to the time t2 can be determined by integrating the tool feed speed F from the time t1 to the time t2. The tool moving along the line A at the feed speed F is kept at the minute speed F min at the start point of the distance L10 in front of the stroke end 2 and moves to the vicinity of the stroke end 2 at the minute speed F min . The maximum speed F max is changed to the minute speed F min by an acceleration constant α set to a given value. A deceleration distance L needed to decelerate to the minute speed F min is determined using the acceleration constant α. A deceleration distance L1 from the maximum speed F max to the minute speed F min can be determined by integrating the tool feed speed F from a time 0 to the time t1. Further, when the tool feed speed F is Fi (< F max ), a deceleration distance L2 from the feed speed Fi to the minute speed F min can be determined by integrating the tool feed speed F from a time t3 when the feed speed F becomes the feed speed Fi to the time t1 along the line A. FIG. 4 is a flowchart showing a processing sequence of the present invention. In FIG. 4, each numeral of the letter "S" represents a step number. [S1] A machining block is preread. [S2] It is determined whether deceleration is necessary or not. That is, it is determined from the preread machining block whether or not the tool moves at the feed speed F greater than the feed speed F min in the vicinity of the stroke end 2 (region within the distance L10 from the stroke end 2) when the machining block is executed. When it is determined that deceleration is necessary because the feed speed F is greater than the minute speed F min , the process goes to step S3, and if not so, the process goes to step S7. [S3] The deceleration distance L is set by the aforesaid method from the feed speed data of the preread machining block and the feed speed F is determined using the thus set deceleration distance L and the acceleration constant α. [S4] The tool is moved at the determined feed speed F. [S5] It is determined whether the tool left the stroke end 2 or not. When the tool left the stroke end 2, the process goes to step S6, and if not so, the process returns to step S4. [S6] Since the tool left the stroke end 2, acceleration is started to carry out an usual feed speed control. [S7] An usual feed speed control is carried out at the control feed speed F controlled in the machining blocks. FIG. 1 is a diagram showing an overall arrangement of an acceleration/deceleration control apparatus for a numerical control apparatus according to the present invention. In FIG. 1, preprocessing means 11 of the numerical control apparatus reads a machining block 18a and supplies the read machining block data (movement data and feed speed data) to stroke end determination means 12. The stroke end determination means 12 determines whether the tool moves beyond the stroke end 2 or not from the machining block data. When the stroke end determination means 12 determines that the tool does not move beyond the stroke end 2 because the feed speed F in the vicinity of the stroke end 2 is equal to or less than the minute speed F min , the movement data of the machining block data is supplied to interpolation means 15 and the feed speed data thereof to acceleration/deceleration prior to interpolation means 14 as they are. On the other hand, when the stroke end determination means 12 determines that the tool moves beyond the stroke end 2 because the feed speed F in the vicinity of the stroke end 2 is greater than the minute speed F min , the stroke end determination means 12 supplies the result of determination to acceleration alteration means 13. Further, the stroke end determination means 12 supplies the feed speed data of the machining block to the acceleration/deceleration prior to interpolation means 14. On receiving the result of determination of the stroke end determination means 12, the acceleration alteration means 13 alters an acceleration prior to interpolation to the preset acceleration constant α and supplies the acceleration constant α to the acceleration/deceleration prior to interpolation means 14. The feed speed data of the machining block data is supplied to the acceleration alternation means 13, whereas the moving data thereof is supplied to the interpolation means 15. The acceleration/deceleration prior to interpolation means 14 subjects the feed speed data supplied from the stroke end determination means 12 to an acceleration/deceleration processing. The acceleration/deceleration processing is carried out based on an acceleration prior to interpolation and the above acceleration constant α. The speed subjected to the acceleration processing is supplied to the interpolation means 15 as speed data multiplied by a linear acceleration/deceleration. The interpolation means 15 determines pulses Xp, Yp, Zp to be distributed to X-, Y-and Z-axes, respectively based on the speed data and the movement data supplied through the stroke end determination means 12. The distributed pulses Xp, Yp, Zp are supplied to X-axis control means 16a, Y-axis control means 16b, and Z-axis control means 16c, respectively and output to motors Mx, My and Mz of the respective axes of a machine tool to execute the drive control of the motors. Note, the acceleration alteration means 13, the acceleration/deceleration prior to interpolation means 14 and the interpolation means 15 function as tool feed speed control means for controlling a tool feed to the minute speed F min based on a result of determination by the stroke end determination means 12 that the tool moves beyond the stroke end 2. As described above, since the tool feed speed F is kept to the minute speed F min in the vicinity of the stroke end 2, a tool can be moved by making maximum use of a stroke and thus a region machinable to the intrinsic stroke of a machine tool can be secured. As described above, according to the present invention, the tool feed speed is kept to the minute speed in the vicinity of the stroke end, the tool can be moved by making maximum use of the stroke so that a region machinable to the intrinsic stroke of a machine tool can be secured.

Claims: An acceleration/deceleration control apparatus for a numerical control apparatus for carrying out acceleration/deceleration control of a tool in the vicinity of a stroke end (2), the apparatus comprising: stroke end determination means (12) for determining whether or not said tool has moved beyond said stroke end; and: tool feed speed control means (13) for controlling a feed speed of said tool so that the feed speed of said tool is set to a minute speed in the vicinity of said stroke end (2) when said stroke end determination means (12) determines that said tool has moved beyond said stroke end; characterised in that: the stroke end determination means makes a determination based upon a pre-read machining block; and said tool feed speed control means (13) determines the feed speed of said tool using a deceleration distance determined from a maximum feed speed of said tool, said minute speed and an acceleration constant.

Inventors: FUJIBAYASHI KENTARO, IDEI TAKASHI, SAGARA SHOICHI, FUJIBAYASHI, KENTARO, IDEI, TAKASHI, SAGARA, SHOICHI, IDEI, TAKASHI FANUC DAI-3 VIRA-KARAMATSU, SAGARA, SHOICHI FANUC DAI-3 VIRA-KARAMATSU
Applicants: FANUC LTD, FANUC LTD.
Application year: 1994
Main classification: G05B19
IPC codes: G05B19